Term
| 3 principle types of synapses |
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Definition
1. electrical
2. fast chemical: via ligand-gated ion channels
3. slow chemical: via metabotropic receptors/2nd messenger systems |
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Term
| How does either type of chemical synapse work? |
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Definition
| transmitter released from presynaptic cell --> crosses to receptor on postsynaptic cell |
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Term
| ______ synapses allow for passive flow of current directly through gap junctions |
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Definition
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Term
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Definition
| aligned paired channels called connexons that create pores for ions to diffuse between the two cells |
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Term
| Each connexon has ______ transmembrane regions |
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Definition
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Term
| One connexon (hemi-channel) is comprised of ______ connexins |
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Definition
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Term
| Each cell expresses ______ that bind together to form a gap junction channel |
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Definition
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Term
| Two hemichannels come together (one from each neuron) to cross about ______ of extracellular space |
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Definition
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Term
| 3 parts of the structure of a connexon |
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Definition
1. 2 extracellular loops (between TMRs 1 & 2 and between TMRs 3 & 4)
2. 4 transmembrane regions that span the membrane
3. 1 cytoplasmic loop in the cytoplasm (between TMRs 2 & 3) |
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Term
| In electrical synapses, cytoplasm is ______ between the two cells |
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Definition
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Term
| How big is the gap between the neurons crossed by an electrical synapse? |
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Definition
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Term
| In electrical synapses, ______ connect presynaptic cytoplasm to postsynaptic cytoplasm |
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Definition
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Term
| Do gap junctions allow flow of electrical current in either direction? |
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Definition
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Term
| Are action potentials necessary for current flow across electrical synapses? |
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Definition
| no! (current will flow regardless of amplitude) |
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Term
| In electrical synapses, the electrical potential in neuron A = ? |
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Definition
| gap potential in neuron B |
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Term
| Are electrical synapses bidirectional? |
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Definition
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Term
| Are electrical synapses extremely fast or extremely slow? |
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Definition
| extremely fast (almost no delay [ < 0.1 ms] between an action potential in the presynaptic neuron & the postsynaptic potential) |
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Term
| Can gap junctions pass both positive & negative current? |
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Definition
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Term
| Are action potentials required for communication across electrical synapses? |
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Definition
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Term
| What is one way to test if two neurons are connected by an electrical synapse? |
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Definition
| inject current into neuron A & it should be mimicked in the voltage readout in neuron A AND in neuron B |
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Term
| three important roles of electrical synapses |
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Definition
1. fast transmission of current
2. synchronize networks of neurons
3. communication between glial cells |
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Term
| Describe the crayfish escape response experiments |
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Definition
| tested by inserting two microelectrodes into the presynaptic lateral giant axon & 2 microelectrodes into the postsynaptic giant motor axon; stimulate presynaptic fiber --> membrane potential spike in postsynaptic axon over length of about 5 ms; stimulate postsynaptic fiber --> small membrane potential spike in presynaptic axon |
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Term
| What type(s) of synaptic transmission is/are present in the chick ciliary ganglion? |
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Definition
| both electrical & chemical |
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Term
| ______ = made by Schwann cells |
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Definition
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Term
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Definition
1. acetylcholine
2. nicotine |
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Term
| example of an NMJ antagonist drug |
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Definition
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Term
| How do NMJ potentiators (ex. neostigmine, physostigmine) work? |
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Definition
| cholinesterase inhibitors |
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Term
| How are synaptic potentials measured in NMJs? |
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Definition
| microelectrode in a muscle fiber that is getting acted upon by a motor axon |
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Term
| EPP amplitude is almost always ______ |
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Definition
| supra-threshold (i.e. triggers an AP) |
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Term
| ______ can be added to reduce amplitude of EPP & "separate" from the muscle AP |
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Definition
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Term
| synaptic delay - peak takes about 1.5 ms; 1/2 decay about 2 ms more...why? |
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Definition
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Term
| If you put a microelectrode in the middle of a muscle fiber, which way will current flow? |
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Definition
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Term
| Do muscle fibers follow the predictions of cable theory? |
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Definition
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Term
| When we remove ______, AP propagates down muscle |
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Definition
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Term
| AP initiated by change in membrane potential at _____ - contraction due to AP |
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Definition
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Term
| What was the setup for the experiment studying the distribution of ACh sensitivity at the frog NMJ? |
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Definition
| intracellular electrode inserted in muscle fiber, ACh pipette dripping ACh into muscle fiber |
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Term
| What happens to ACh sensitivity as you get farther away from the edge of the NMJ terminal? |
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Definition
| it gets less (less membrane voltage increase) |
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Term
| For the NMJ of the snake, which region has the highest ACh sensitivity? |
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Definition
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Term
| For the NMJ of the snake, which region has dramatic ACh sensitivity decreases the farther you get from the edge of the crater? |
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Definition
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Term
| For the NMJ of the snake, which region has the lowest ACh sensitivity? |
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Definition
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Term
| two extracellular components to the AChR subunit structure |
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Definition
1. NH2 loop connected to the M1 TMR
2. COOH coming off of the M4 TMR |
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Term
| AChR subunits have _____ TMRs |
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Definition
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Term
| two cytoplasm loops in the AChR subunit |
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Definition
1. big cytoplasm loop between M3 & M4
2. tiny cytoplasm loop between M1 & M2 |
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Term
| where is the tiny extracellular loop in the AChR subunit located? |
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Definition
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Term
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Definition
| two alpha, one beta, one gamma, one delta |
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Term
| Is each ACh receptor subunit a TMR? |
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Definition
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Term
| ______ ACh molecules must be bound to an AChR & then channel will open to be in conducting state --> current will pass |
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Definition
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Term
| two conformations in which nAChRs are not conducting |
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Definition
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Term
| conformation in which nAChR is conducting |
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Definition
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Term
| Total end plate current is sum of ______ |
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Definition
| individual channel currents |
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